A cardiac arrhythmia is a condition in which the heart's normal rhythm is disrupted. There are many types of cardiac arrhythmias, including supraventricular arrhythmias that begin above the ventricles (such as premature atrial contractions, atrial flutter, accessory pathway tachycardias, atrial fibrillation, and AV nodal reentrant tachycardia), ventricular arrhythmias that begin in the lower chambers of the heart (such as premature ventricular contractions, ventricular tachycardia, ventricular fibrillation, and long QT syndrome), and bradyarrhythmias that involve slow heart rhythms and may arise from disease in the heart's conduction system.
Certain types of cardiac arrhythmias, including ventricular tachycardia and atrial fibrillation, may be treated by ablation (for example, radiofrequency (RF) ablation, cryoablation, hot balloon ablation, ultrasound ablation, laser ablation, microwave ablation, and the like), either endocardially or epicardially. For example, atrial fibrillation (AF) is frequently treated with pulmonary vein ablation (also called pulmonary vein antrum isolation, or PVAI), a procedure that involves positioning a treatment element, such as a cryoballoon or hot balloon (for example, the Toray-Satake balloon), at the mouth or ostium of a pulmonary vein such that the treatment element is in contact with an circumferential area of cardiac tissue at the ostium. After ablation of the ostial tissue, cardiac tissue, such as within or surrounding the pulmonary vein, may be mapped to confirm pulmonary vein isolation. That is, mapping may be used to determine whether aberrant electrical conductivity is still present. For example, a system such as the ARCTIC FRONT® over-the-wire cryoablation catheter system with the ACHIEVE® mapping catheter (both from Medtronic Inc., Minneapolis, Minn.) includes pulmonary vein ablation and mapping functionality.
When a cryoballoon or hot balloon is used as the treatment element in a PVAI procedure, it is desirable that the balloon is in complete contact with the pulmonary vein ostial tissue so as to totally occlude the pulmonary vein. However, ostial sizes can vary greatly, both within the same patient (for example, each of the patient's pulmonary vein ostia may be a different size) and between patients. Currently, a surgeon must have a multitude of differently sized catheters on hand in order to accommodate this variety. Further, a surgeon may have to try several non-reusable catheters to find the right fit, which can be costly and time consuming.
It is therefore desirable to provide a system that includes a treatment element that is adjustable to accommodate any of a variety of ostial sizes.